1. Field of the Invention
The present invention relates to an object detecting device for detecting an object ahead of a vehicle in the direction of its movement. This detection is based on the reception of a reflected wave, resulting from the reflection from the object, of an electric wave transmitted ahead of the vehicle. The invention is also directed to a travel safety system for a vehicle, including such an object detecting device.
2. Description of the Related Art
There is a travel safety system known from Japanese Patent Application Laid-open No. 11-202049, wherein a radar device mounted on a subject vehicle detects a distance to an obstacle such as a vehicle traveling ahead of the subject vehicle, and a direction and a relative speed of the obstacle. When it is determined that there is a possibility of the contact of the subject vehicle with the obstacle, based on the distance, the direction and the relative speed, a warning is provided to a driver to instruct spontaneous braking or steering, or an automatically braking device is operated. Thus the subject vehicle can be prevented from coming into contact with the obstacle, or alleviating the damage due to the contact.
When a millimeter wave radar device is used, information on distances to a plurality of objects, directions and relative speeds of the objects can be obtained. If information on a vehicle speed of the subject vehicle is added to such information, an object with a speed relative to the subject vehicle that is equal to the vehicle speed of the subject vehicle can be recognized as a stationary object at rest on a road surface. Examples of such stationary objects include dropped objects on a road surface (such as an iron plate, a corrugated board, an opened can and the like) in addition to a footbridge and a signpost. For those of these dropped objects, which have a height of, for example, about 10 cm, there is no possibility that even if the vehicle travels astride the objects, the objects come into contact with a lower surface of the vehicle and hence, there is particularly not a hindrance.
With the known safety system, however, it is impossible to distinguish a stationary object such as a dropped object of a small height which provides no hindrance even if the vehicle passes over the object, from another large-sized stationary object the contact of the vehicle with which is required to be avoided. For to this reason, an unnecessary warning or an unnecessary automatic braking may be produced that provides difficulty for a driver in some cases.
Accordingly, it is an object of the present invention to ensure that it is possible to precisely determine whether an object detected by an object detecting means is an object which provides no hindrance even if the vehicle passes over the object, or as an object the contact of the vehicle with which is required to be avoided.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an object detecting device comprising a transmitting means for transmitting an electric wave in a direction of movement of a vehicle, a receiving means for receiving a reflected wave resulting from a reflection of the electric wave transmitted by the transmitting means from an object, and an object detecting means for detecting whether the object is on a course for the vehicle, based on a result of a reception provided by the receiving means, wherein the object detecting device further includes an obstacle determining means for determining whether the object detected by the object detecting means is an obstacle which provides a hindrance to the movement of the vehicle.
With the above arrangement, when the object detecting means detects the object based on the result of the reception of the reflected wave resulting from the reflection from the object of the electric wave transmitted in the direction of movement of the vehicle, the obstacle determining means determines whether the object is an obstacle which provides a hindrance to the movement of the vehicle. Therefore, it is possible to precisely determine whether it is necessary to conduct an operation for avoiding contact of the vehicle with the object, or whether the vehicle may pass over the object as it is.
According to a second aspect and feature of the present invention, the object detecting device further includes a motional state detecting means for detecting a motional state of the vehicle, and a stationary object determining means for determining whether the object detected by the object detecting means is a stationary object, based on the motional state of the vehicle detected by the motional state detecting means and the result of reception provided by the receiving means, and wherein the obstacle determining means determines whether the object determined as being the stationary object by the stationary object determining means is an obstacle.
With the above arrangement, it is determined whether the object is an obstacle, based on the motional state of the vehicle and the result of reception provided by the receiving means, and it is determined whether the object determined as being the stationary object is an obstacle. Therefore, the obstacle over which the vehicle cannot stride is excepted in advance, thereby simplifying the determination of whether the object is an obstacle which provides a hindrance to the movement of the vehicle.
According to a third aspect and feature of the present invention, the obstacle determining means determines that an object detected with a level of a signal received by the receiving means at a short distance being equal to or lower than a predetermined value is an object which provides no hindrance to the traveling of the vehicle.
With the above arrangement, the object detected with the level of the signal received by the receiving means at the short distance being equal to or lower than a predetermined value is determined as being the object which provides no hindrance to the traveling of the vehicle. Therefore, it is possible to precisely determine whether the object is an obstacle, in accordance with the level of the received signal.
The xe2x80x9cshort distancexe2x80x9d is set to a distance in a range of about 10 m to about 20 m in an embodiment, but is not limited to a distance in such range in the present invention.
According to a fourth aspect and feature of the present invention, the obstacle determining means determines that an object detected with a rate of decrease in the level of a signal received at a short distance being equal to or higher than a predetermined value is an object which provides no hindrance to the traveling of the vehicle.
With the above arrangement, the object detected with the rate of decrease in the level of the signal received at the short distance being equal to or higher than the predetermined value is determined as being the object which provides no hindrance to the traveling of the vehicle. Therefore, it is possible to precisely determine whether the object is an obstacle, in accordance with the rate of decrease in the level of the received signal.
The xe2x80x9cshort distancexe2x80x9d is set to a distance in the range of about 10 m to about 20 m in the embodiment, but is not limited to a distance in such range in the present invention.
According to a fifth aspect and feature of the present invention, the object detecting device further includes a scattering determining means for determining a scattering in the level of a signal received by the receiving means, and the obstacle determining means determines that an object detected with the scattering determined by the scattering determining means being equal to or smaller than a predetermined value is an object which provides no hindrance to the movement of the vehicle.
With the above arrangement, the object detected with the scattering determined by the scattering determining means being equal to or smaller than the predetermined value is determined as being the object which provides no hindrance to the movement of the vehicle. Therefore, it is possible to precisely determine whether the object is an obstacle, in accordance with the scattering in the level of the received signal.
According to a sixth aspect and feature of the present invention, the scattering determining means determines a scattering in the level of the signal received by the receiving means for an object spaced at a predetermined distance from the vehicle.
With the above arrangement, the scattering in the level of the signal received by the receiving means is determined for the object spaced at a predetermined distance from the vehicle. Therefore, the difference between the scatterings is remarkable depending on the height of an object, and it is possible to precisely determine an object that provides no hindrance to the traveling of the vehicle.
The xe2x80x9cpredetermined distancexe2x80x9d is set in a range of 20 m to 100 m in the embodiment, but is not limited to a distance in such range in the present invention.
According to a seventh aspect and feature of the present invention, the scattering determining means determines a scattering in the signal received by the receiving means in a predetermined time.
With the above arrangement, the scattering in the signal received by the receiving means in the predetermined time is determined. Therefore, an influence such as a noise can be eliminated to accurately determine the scattering.
The xe2x80x9cpredetermined timexe2x80x9d is set in a range of 0.5 seconds to 2.0 seconds in the embodiment, but is not limited to a time in such range in the present invention.
According to an eight aspect and feature of the present invention, there is provided a travel safety system for a vehicle, including an object detecting device having the first or second feature, wherein when there is a possibility of contact of the vehicle with an object detected by the object detecting device, the safety system mounted in the vehicle is operated to avoid the contact, wherein when the obstacle determining means determines that the object is an object which provides no hindrance to the movement of the vehicle, the operation of the safety system is discontinued or moderated.
With the above arrangement, when the detected object is the object which provides no hindrance to the movement of the vehicle, the operation of the safety system for avoiding the contact of the vehicle with the object is discontinued or moderated. Therefore, it is possible to avoid having a driver receive a sense of incompatibility due to an unnecessary operation of the safety system.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.